AssignFile 过程
使外部文件的名字与file变量关联
单元
System
种类
文件管理程序
Delphi 语法：
procedure AssignFile(var F; FileName: string);
详细内容：
Call AssignFile to initialize a file variable in Delphi code.
在delphi代码里调用AssignFile初始化一个file变量
F is a file variable of any file type. FileName is a string-type expression or an
expression of type PChar if extended syntax is enabled.
F是一个file类型的变量，FileName是string-type的表达式，如果扩展语法开关是开启的，那么PChar
类型也允许使用的
After calling AssignFile, F is associated with the external file until F is closed. All
further operations on the file variable F operate on the external file named by FileName.
在调用AssignFile后,在F没有关闭之前，变量F将一直与外部文件关联。所有更多对file变量F的操作都
将对应发生在文件名为FileName的外部文件上。
When the FileName parameter is empty, AssignFile associates F with the standard input or
standard output file. If assigned an empty name, after a call to Reset (F), F refers to
the standard input file, and after a call to Rewrite (F), F refers to the standard output
file.
假如FileName参数是空的，AssignFile将F与标准输入或者标准输出文件关联。假如赋值一个空的名字
，在调用Reset(F)之后，F将引用标准输入文件，而调用Rewrite(F)之后，F将引用标准输出文件。
Do not use AssignFile on a file variable that is already open.
不要将AssignFile用在已经打开的File变量上。
Note: To avoid scope conflicts, AssignFile replaces the Assign procedure that was
available in early versions of the Delphi product. However, for backward compatibility
Assign is still available.
注意：为了避免范围冲突，AssignFile将取代在delphi较早版本中的Assign存储过程，为了向后兼容As
sign仍然有效。
available in early versions of the Delphi product. However, for backward compatibility Assign is still available.